The invention relates to a method and an apparatus for detecting paper material of paper and, more particularly, to a method and an apparatus for paper material discrimination of an apparatus which handles paper such as securities, bill, or the like.
As a method of detecting a paper material of paper, at disclosed in JP-A-8-180189, there is a technique made by paying attention to a peculiar structure of paper fibers which are formed in a manufacturing step of the paper. According to such a technique, a lattice-like light/dense pattern which is derived from the structure (regular pattern which is laced into paper) that is peculiar to a specific bill is fetched and data is analyzed, thereby discriminating the paper material. As disclosed in JP-A-11-139620, there is also a method of discriminating a paper material from a time that is required for conveying paper for a predetermined distance by using a principle such that friction upon conveyance differs depending on a paper material of a paper.
As disclosed in JP-A-10-232166, there is a technique regarding a discriminating method of a paper pack whereby a material of the paper containing no metal can be discriminated. According to such a technique, by irradiating a near-infrared light onto the paper pack and specifying a wavelength at a peak of absorbance of a wavelength of the non-infrared light that is peculiar to the material, a kind of paper pack is discriminated.
The lattice-like light/dense pattern to which the attention has been paid in JP-A-8-180189 is laced into the paper which is used for the bill to identify the authentic bill. However, even in case of the same paper material, if the manufacturing steps are different, the light/dense pattern changes. There is, consequently a problem such that the paper material cannot be precisely discriminated by one data analyzing method due to an influence by a variation of the lattice-like light/dense patterns. According to the technique of JP-A-11-139620, there is a problem such that since a degree of the friction or hardness of the paper fluctuates due to an influence by humidity, a deterioration of the paper material, or the like, such a technique can be applied only in a limited situation.
Further, according to the technique of JP-A10-232166, in order to specify the wavelength at the peak of the absorbance, amounts of all of the reflection lights within a range prom 800 nm to 2500 nm have to be obtained. There is, consequently, a problem such that a time which is required for such a purpose is too long with respect to the paper such as securities, bill, or the like in which a high speed process is necessary.
It is an object of the invention to provide a technique for discriminating a paper material independent of a light/dense pattern with is caused by a difference of manufacturing steps. Another object of the invention is to provide a technique for discriminating a paper material of paper without being influenced by humidity or paper material. Further another object of the invention is to provide a technique for making a precise discrimination of a paper material at a high speed. Other objects will be obviously understood from the following detailed description.
According to the invention, lights of different kinds of wavelengths are irradiated onto paper and absorbances of reflected lights are measured, thereby discriminating, the paper material of the paper from a difference between the absorbances. More specifically speaking, absorbances in two infrared lights of different wavelengths are obtained and the paper material is discriminated by a degree of difference between the absorbances, that is, an absorbance difference or an absorbance ratio.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiment of the invention taken in conjunction with the accompanying drawings.